/usr/obj/pkgsrc/www/firefox/work/mozilla/security/nss/lib/freebl/prng_fips1861.c,
line 397:
/*
* Initialize the global RNG context and give it some seed input taken
* from the system. This function is thread-safe and will only allow
* the global context to be initialized once. The seed input is likely
* small, so it is imperative that RNG_RandomUpdate() be called with
* additional seed data before the generator is used. A good way to
* provide the generator with additional entropy is to call
* RNG_SystemInfoForRNG(). Note that NSS_Init() does exactly that.
*/
SECStatus
RNG_RNGInit(void)
{
/* Allow only one call to initialize the context */
PR_CallOnce(&coRNGInit, rng_init);
/* Make sure there is a context */
return (globalrng != NULL) ? PR_SUCCESS : PR_FAILURE;
}

and in
/usr/obj/pkgsrc/www/firefox/work/mozilla/security/nss/lib/freebl/loader.c
line: 923: